Over many decades, the evidence has been accumulating that cholesterol is related to heart disease, particularly angina and heart attacks. Numerous studies now show that the higher a populations' average cholesterol level, the more frequently heart disease occurs in that population.

Animal studies are also indicative. Rabbits fed cholesterol showed that some of the dietary cholesterol gets deposited in the arteries, and this is what causes "hardening of the arteries" and narrowing of the arteries, known as arteriosclerosis or atherosclerosis. This then results in decreased blood flow to the heart muscle, which leads to chest pain during exercise or other stresses (angina) and/or heart attacks.

Another link between cholesterol and heart disease is seen in people with inherited disorders of cholesterol, such as familial hypercholesterolemia. Individuals with this inherited high level of cholesterol develop heart disease early in life. For example, if an individual inherits two genes for this disorder, extensive narrowing of the arteries can occur as early as 5 to 6 years of age.

Most importantly, clinical trials using cholesterol-lowering regimens, either diet or drugs, have shown a significant reduction in cardiac problems, including angina and heart attack.

The benefit of lowered blood cholesterol in preventing angina and heart attack has been shown in many large studies. In the Lipid Research Clinic Study, for every 1% decrease in blood cholesterol, there was 2% decrease in the likelihood of a heart attack. In people who suffer from angina or have had a heart attack, lowering of LDL-cholesterol not only decreased the frequency of subsequent episodes (including stroke) but also increased their overall survival.